Camshaft phasers for varying the timing of combustion valves in internal combustion engines are well known. A first element, known generally as a sprocket element, is driven by a chain, belt, or gearing from the crankshaft of the internal combustion engine. A second element, known generally as a camshaft plate, is mounted to the end of a camshaft of the internal combustion engine. A common type of camshaft phaser used by motor vehicle manufactures is known as a vane-type camshaft phaser. U.S. Pat. No. 7,421,989 shows a typical vane-type camshaft phaser which generally comprises a plurality of outwardly-extending vanes on a rotor interspersed with a plurality of inwardly-extending lobes on a stator, forming alternating advance and retard chambers between the vanes and lobes. Engine oil is supplied via a multiport oil control valve, in accordance with an engine control module, to either the advance or retard chambers, to change the angular position of the rotor relative to the stator, and consequently the angular position of the camshaft relative to the crankshaft, as required to meet current or anticipated engine operating conditions.
While vane-type camshaft phasers are effective and relatively inexpensive, they do suffer from drawbacks such as slow operation at low engine speeds due to low oil pressure, slow operation at low engine temperatures due to high oil viscosity, increased oil pump capacity requirement for the oil pump used to lubricate the internal combustion because the same pump is used to actuate the vane-type camshaft phaser, and the total amount of phase authority provided by vane-type camshaft phasers is limited by the amount of space between adjacent vanes and lobes and may not be sufficient to provide the desired amount of phase authority. For at least these reasons, the automotive industry is developing electrically driven camshaft phasers.
One type of electrically driven camshaft phaser being developed uses a harmonic gear drive unit, actuated by an electric motor, to change the angular position of the camshaft relative to the crankshaft. One example of such a camshaft phaser is shown in United States Patent Application Publication No. US 2012/0312258 A1 to Kimus et al. and U.S. Pat. No. 8,516,983 to David et al., the disclosures of which are both incorporated herein by reference in their entirety. While the camshaft phasers of Kimus et al. and David et al. may be effective, the disclosed camshaft phasers are mounted to the camshafts by bolting the camshaft phasers to the axial end of the camshafts. Some internal combustion engines utilize a camshaft with a timing sprocket secured thereto which is driven by a chain from the camshaft. The timing sprocket may be located axially between camshaft bearings which support the camshaft. The camshaft phasers of Kimus et al. and David et al. are not suitable for such a camshaft, timing sprocket, and camshaft bearing arrangement because bolting the camshaft phasers of Kimus et al. and David et al. to the axial end of the camshaft does not allow proper positioning of the camshaft phaser to connect to the chain to the corresponding sprocket of the camshaft phaser. Consequently, a significant redesign of the internal combustion engine would be necessary in order to mount the camshaft phasers of Kimus et al. and David et al. Such a redesign may be time consuming and costly to accomplish.
What is needed is a camshaft phaser which minimizes or eliminates one or more of the shortcomings as set forth above.